Possible Clues:

• Walk with an injury
• Exhibit a sore leg
• Lacking backbone, the Colonel lost his head
• Feeble record I am cutting
• After just over half a century a Parliamentarian is not a big stiff
• Walk stiffly - lacking energy
• Sluggish learner associated with young devil
• Far from firm line taken with brat
• Drag one's feet? That's not hard
• There's trouble afoot in so slack a way